Ink jet recording heads are examples of liquid discharge heads that are generally known. Referring to FIGS. 11A to 11C, a structure of an ink jet recording head is briefly described.
As shown in FIG. 11A, an ink jet recording head H1001 includes a tank holder unit H1003 and a recording element unit H1002 for discharging ink.
Ink is supplied from an ink tank (not shown) to a recording element unit H1002 through an ink flow path formed in the tank holder unit H1003.
The ink flow path is formed in the tank holder unit H1003 by joining a tank holder H1500 shown in FIG. 11B to a flow path forming member H1600 shown in FIG. 11C.
Known methods for joining the tank holder H1500 to the flow path forming member H1600 include ultrasonic welding (Patent Citation 1) and laser welding (Patent Citation 2).
Among the methods, the laser welding method is described. The term “laser welding” generally refers to a method of making a member being transparent to a laser beam and a member being capable of absorbing a laser beam contact each other and irradiating a region to be welded with a laser beam so as to join the members together.
As compared with ultrasonic welding, laser welding has an advantage in that foreign matter is negligibly generated at the welded portion and is used as effective means for forming an ink flow path.
Referring to FIGS. 12A to 13C, a method of joining a tank holder H1500 to a flow path forming member H1600 by laser welding described in Patent Citation 2 is explained. FIGS. 13A to 13C are schematic sectional views of the tank holder H1500 and the flow path forming member H1600 shown in FIGS. 12A and 12B.
The tank holder H1500, which is capable of absorbing a laser beam, and the flow path forming member H1600, which is transparent to a laser beam, are made to contact each other using a press jig 510 (FIGS. 12A and 13A). Then, while the tank holder H1500 and the flow path forming member H1600 are in contact with each other, a contact surface 600 is irradiated with a laser beam (FIGS. 12B and 13B), so that an ink flow path is formed (FIG. 13C).
Examples of laser irradiation methods include a scanning method described in Patent Citation 2 and a simultaneous irradiation method.
By the scanning method, a desired junction surface is irradiated with a laser beam along a locus in a scanning manner by concentrating the spot diameter of the laser beam emitted from a laser irradiation apparatus 500 as shown in FIGS. 12B and 13B.
By the simultaneous irradiation method, a desired junction surface is irradiated with a laser beam in one go.    [Patent Citation 1] Japanese Patent Laid-Open No. 2007-283668    [Patent Citation 2] U.S. Pat. No. 7,261,397